Step Up Your Game: Multi-Board Versus Multilayer Designs

I don’t remember much about playing football in high school. I’m not sure if that’s because of wanting to forget the endless grueling practices to prepare us for getting pummeled in the game, or actually getting pummeled in the game. Either way, I tend to vaguely associate high school football with lots of hard work and pain, punctuated by the occasional moments of glory. If there is one thing that I do remember very vividly, it was the coaches encouraging us to always “step up our game”.

Our coaches knew that the goal wasn’t a matter of arriving at a plateau, but instead constantly advancing to the next level. To prepare us, therefore, for whatever was coming next, they pounded “step up your game” into our heads every moment that they could, and I’m actually grateful for that. It helped me through my teenage year and continues to help me today. In my career of designing circuit boards, I have had to step up my game many times. I’ve seen advances from thru-hole technology to surface mount, and from wide open designs to high density interconnect (HDI) designs. Now the next step has arrived: moving up from designing single multilayer boards to designing multi-board systems.

Those of us in the design world are familiar with designing a single printed circuit board, but designing multiple boards for a system is probably something new to many of us. Fortunately, there are new and enhanced PCB design CAD tools that can help with this task. Whereas designing PCBs for a multi-board system used to be a clumsy manual process, these new tools provide a design solution that is eloquent and actually fun to use. Keep reading and you’ll see what I mean.

Today’s PCB designs often require designing all of the system boards together

Remembering the Old Ways

System level design is nothing new, but how we design the different circuit boards that make up a system is. For years, PCB design was limited to designing one board at a time as there wasn’t a CAD solution that would design multiple system boards together. The mechanical design of the system would dictate the size and shapes of the different circuit boards that would fit into it, but the boards would be designed individually.

After individual PCBs were designed, they would be built as prototypes. Once these prototypes were up and running, they would then be put together as an entire system. This would allow system level electrical and mechanical checking to be run. Any problems discovered would have to be sent back to the design engineers for another spin of the boards. I have worked on designs in systems like this that required major changes to board outline shapes and component placement in order to make the board work with the rest of the system. It was a tedious process, to say the least.

A Step in the Right Direction

As 3D mechanical CAD systems grew in their abilities, they became an important part of the design process. They could create the board outline shape with the appropriate keepout and mechanical clearance zones, and send that data to the PCB design CAD system. Once the printed circuit board was designed, they could then read the PCB design placement and library files in order to accurately depict the populated circuit board within the system.

Mechanical CAD systems were a major step forward towards total system design. Design teams could now check for physical conflicts between the board and the rest of the system before building prototype boards. However, there still wasn’t a way to verify electrical connections, and all changes and corrections still had to be sent back to the individual PCB designs.

Today, system level design is a whole lot easier due to the ability to create multi-boards at the PCB design level. Where PCB design systems in the past could only create individual designs, you can now link together multiple board designs in one multi-board project. This makes it possible for individual board designs to be treated as child objects within the main system assembly.

Interconnections between the boards are identified for electrical checking by assigning multi-board properties to connecting nets on the schematic. In this way, the PCB design system knows how the system boards are connected just as if they are physically connected together in the actual system. This facilitates electrical checking to verify that intra-board connectors have the correct pin assignments.

In the 3D environment of the PCB layout tools, the different system boards can be brought together within their enclosure. This allows for physical conflict clearance checking as well as checking for the correct location of interconnecting components such as plugs and connectors. Any changes that are required can be made at the 3D system level in order to verify that all connectors are aligned correctly and any physical conflicts have been resolved.

Multi-board design in today’s PCB design CAD tools is not just a step up in your game; it is a complete game changer. You will save time and money previously spent on system prototypes by confirming beforehand that your circuit boards are system ready.